It could be something simple but it'll still cost you to find out.
First, shine a torch through the front cassette flap and check for foreign objects obstucting the mechanism.
eg. label off a cassette, stuck in mechanism,..is very common.
Otherwise, unless it's a quailty brand and spec. eg. maybe has twin tuners instead of the usual single tuner, I'd buy a new one.
Combi TV/VCR generally take longer to disassemble and repair than seperate units and it inevitably puts up repair charges.
It may cost less to repair than replace but the rest of the unit is as old as it ever was and a new unit obviously gets you all new shiney parts, new remote and a full manufacturers warranty.
Cobweb, November 2005